Probability that a fossil absent from a sample is also absent from the paleolandscape

A procedure to calculate probability limits for the inference that the abse nce of a taxon from a woodrat (Neotoma) midden implies absence from the pal eolandscape uses paired samples of modern vegetation communities and paired samples of paleocommunities. Assumptions are: (1) each member of a sample pair is an independent measure of the same vegetation assemblage; (2) behav ioral patterns of woodrats are the same as each midden in a paired sample i s constructed; and (3) the probability of fossilization is zero when a taxo n is absent from the vegetation. The procedure provides a logical test of d ata consistency: the upper probability limit of making a false inference sh ould be greater than the lower limit. Averaged over 140 plant taxa, the upp er and lower probability limits for a false inference were 11 and 7%, respe ctively. More than 70% of taxa passed the logical test, indicating a reliab le procedure. For many taxa that failed the logical test, four potential ex planations account for this failure, two of which can be solved by simply i ncreasing sample sizes. Using analogous assumptions, the procedures are app licable to other types of stratigraphic sampling such as macrofossils from sediment cores or fossils from biostratigraphic units. (C) 2000 University of Washington.